Assignment 9, Due at 11:59pm, Friday Dec 05. (Absolute deadline!)

Objectives

• Implement a Splay Tree's function.
• This is a chance to delve deeper into implementing a "real" data structure.
• Getting more comfortable with pointers.

What to do

You are to write a C++ program that does the following.

1. It keeps reading user's inputs, line by line. Each input line the user types is supposed to be in one of the following forms:

   newtree
   insert [list of integer keys]
   remove [key]
   find [key]
   insert [key]
   print
   exit
   

   where
   • exit tells your program to quit
   • newtree creates a new Splay Tree and clear the old tree.
   • [key] is any integer such as 5 or -3
   • [list of integer keys] is a list of integers separated by spaces, such as 5 -3 4 1 20.
   • insert inserts the list of keys (integers) into a Splay tree. If the key already exists in the tree then it is not inserted.
   • remove removes a node with the key from the Splay tree. If the key does not exist in the tree then we report so.
   • find returns whether the key exists in the tree
   • print prints the tree in pretty format
2. I have written most of the above program, leaving out two functions: splay() and remove(). You can download the source codes by typing (from your timberlake account):

   wget http://www.cse.buffalo.edu/~hungngo/classes/2014/Fall/250/assignments/A9.tar.gz
   gunzip A9.tar.gz
   tar -xvf A9.tar
   cd A9
   make
   

   An executable named splaydriver will be produced. I've already implemented the assignment. You can download the binary and run it under timberlake

   wget http://www.cse.buffalo.edu/~hungngo/classes/2014/Fall/250/assignments/hqn-splaydriver
   chmod 700 hqn-splaydriver
   

   Here is a sample run of splaydriver:

   $ hqn-splaydriver
   UB Splay Tree Driver. Version 0.7
    hqn
    Please report bugs to hungngo@buffalo.edu
   
   > insert 50 40 30 20 10
   50 just inserted
   40 just inserted
   30 just inserted
   20 just inserted
   10 just inserted
   > print
     [10]
    /    \
   x    [20]
       /    \
      x    [30]
          /    \
         x    [40]
             /    \
            x    [50]
   > find 50
   50 FOUND
   > print
            _[50]_
           /      \
       _[20]_      x
      /      \
   [10]     [40]
           /    \
        [30]     x
   > find 45
   45 NOT FOUND
   > print
           [40]_
          /     \
       [20]    [50]
      /    \
   [10]   [30]
   > insert 32
   32 just inserted
   > print
               _[32]_
              /      \
           [30]     [40]
          /    \   /    \
       [20]     x x    [50]
      /    \
   [10]     x
   > insert 25
   25 just inserted
   > print
           __[25]__
          /        \
       [20]       [32]
      /    \     /    \
   [10]     x [30]   [40]
                    /    \
                   x    [50]
   > remove 25
   25 removed!
   > print
               _[32]_
              /      \
           [30]     [40]
          /    \   /    \
       [20]     x x    [50]
      /    \
   [10]     x
   > remove 31
   ** ERROR **
   Key 31 NOT removed
   
   > print
           _[30]_
          /      \
       [20]     [32]
      /    \   /    \
   [10]     x x    [40]
                  /    \
                 x    [50]
   > remove 32
   32 removed!
   > print
           _[30]_
          /      \
       [20]     [40]
      /    \   /    \
   [10]     x x    [50]
   > remove 20
   20 removed!
   > print
       [30]
      /    \
   [10]   [40]
         /    \
        x    [50]
   > remove 50
   50 removed!
   > print
           [40]
          /    \
       [30]     x
      /    \
   [10]     x
   > remove 40
   40 removed!
   > print
       [30]
      /    \
   [10]     x
   > remove 10
   10 removed!
   > print
   [30]
   > remove 30
   30 removed!
   > print
   > exit
   

3. Finally, the only file you can modify is SplayTree.cpp. You are to supply the body of the two functions that have TODO: TBD in the body. I strongly suggest you read the rest of the code base carefully before starting. In particular, make sure you understand what leftRotate() and rightRotate() do. Do not modify any other functions' bodies. Do not add any more data members nor function members.
4. When you submit your assignment, you will only submit one file: SplayTree.cpp. We will copy this file to a directory containing all other files and compile and grade. Don't modify any other files.

How to submit

submit_cse250 SplayTree.cpp

Note that the above line only works if you logged in to your CSE account and the file is there. All previous things can be done at home, as long as you remember to upload the final file to your CSE account and run the submit script from there.

Grading

• 0 point if your SplayTree.cpp does not compile with the other files intact.
• 10 points if your SplayTree.cpp file does compile. In other words, if you don't do anything, just re-submit the file, you'll get 10 points.
• 30 points if remove() works correctly (with or without splaying). Remember to delete the pointer to the node that's removed, else you'll get a memory leak.
• 30 points if splay() works correctly. Since insert and find calls splay, we can test if your splay function works correctly by looking at the tree printed after insert or find.
• 30 points if remove() works correctly with splaying. In particular, the correct node is splayed up to the root after a removal. And, if we try to remove a node that is not found, then the node right before we hit the NULL pointer is splayed. (Read the code base!) Please run my implementation to see how the tree is supposed to look like after a removal.